Threads, especially screw threads, are sensitive to damage caused by impact, due to their sharp crests which are easily nicked or otherwise deformed and which, when so damaged, make it difficult to apply nuts or other matching parts. Experienced mechanics are careful not to apply such components forcibly, as their own threads might be damaged in the process. Damaged screw threads should therefore be repaired before, say, reassembly of threaded components. While, in principle, screw threads can be repaired with the aid of threading dies, this could necessitate the acquisition of several large and expensive sets of dies, one set for each of the several thread standards of which, in automotive applications alone, there are at least five. For the average workshop or garage, not to speak of the “do-it-yourself” man in his basement shop, this is quite impractical. It is, of course, also possible to use a triangular file for screw thread repair; this, however, requires a considerable amount of skill, is time-consuming and mostly yields poor results.
Such a tool is disclosed in U.S. Pat. No. 5,060,330, obtained by the present Applicant and incorporated herein by reference.
While this prior-art tool indeed constitutes a considerable improvement on other existing tools, it is not only relatively bulky and heavy, but the absence of any guiding element for the cutters is liable to cause difficulties, in particular with heavily damaged threads.